The invention relates generally to the field of ultrasound imaging, and in particular, to the imaging of body lumens with ultrasound imaging catheters.
Physicians make use of catheters today in medical procedures that are best performed by gaining access into interior regions of the body. For example, in electrophysiological therapy, ablation is used to treat cardiac rhythm disturbances. Such a therapy may be used, for example, to treat atrial fibrillation by forming long, thin lesions of different curvilinear shapes in heart tissue.
During these procedures, a physician steers a catheter through a vein or artery into the interior region of the heart that is to be treated. An ablation element carried on the distal end of the catheter is positioned near the tissue that is to be ablated. For such treatments, the delivery of ablating energy must be closely governed to avoid incidence of tissue damage and coagulum formation. Further, the ablation catheters must be precisely positioned adjacent to and preferably in contact with the tissue to be treated, to ensure the lesions are properly located.
Physicians and staff performing diagnostic and therapeutic procedures, such as electrophysiological therapy, typically require an imaging system to assist them in positioning the ablation catheter. Mini-transesophageal echocardiography (mini-TEE) probes are available, however, these probes must be swallowed or inserted down the patient's throat. Such probes are poorly tolerated by patients unless they are fully anesthetized. Further, these probes can be rather large (i.e., 20 French in diameter), use complex transducer configurations and are costly enough to discourage their disposal after a single use.
Alternatively, the use of ultrasound imaging systems, and in particular ultrasound imaging catheters, would be particularly useful in helping physicians monitor the positioning of ablation catheters. It is desirable, therefore, to have an ultrasound imaging catheter small enough to enter narrow and tortuous regions of the patient's vascular system. It also is desirable if such imaging systems were easy to operate and cost efficient to encourage their disposal after use.